1. Field of the Invention
The present invention relates to an optical system driving control device adapted for a photographic camera using a silver-halide film on a photo-taking plane or for a still camera or a video camera using a CCD as an image sensor, and also to an optical apparatus using the optical system driving control device.
2. Description of Related Art
Known photo-taking apparatuses (optical apparatuses) of the kind having a magnification varying action of a photo-taking optical system and that of a viewfinder optical system arranged to be performed in association with each other include, for example, cameras disclosed in Japanese Laid-Open Patent Application No.
HEI 7-64141 and Japanese Laid-Open Patent Application No. HEI 5-333406.
The camera disclosed in Japanese Laid-Open Patent Application No. HEI 7-64141 is arranged to have a lens driving mechanism used mechanically in common for a photo-taking optical system and a viewfinder optical system. More specifically, a cam tube is arranged to be used as a lens driving mechanism in common for the photo-taking optical system and the viewfinder optical system and to be rotated and driven by a motor for a magnification varying action of the photo-taking optical system and also for that of the viewfinder optical system.
In the case of the camera disclosed in Japanese Laid-Open Patent Application No. HEI 5-333406, a photo-taking optical system and a viewfinder optical system are provided respectively with zoom driving mechanisms and driving motors for driving the zoom driving mechanisms. When the camera is loaded with a film, a microcomputer controls the driving motor of the photo-taking optical system and that of the viewfinder optical system in such a way as to cause the photo-taking optical system and the viewfinder optical system to perform their magnification varying actions in association with each other. In a case where the camera is not loaded with any film, the microcomputer controls the driving motor of the viewfinder optical system to cause only the viewfinder optical system to perform the magnification varying action.
In the camera disclosed in Japanese Laid-Open Patent Application No. HEI 7-64141, the magnification varying action of the photo-taking optical system and that of the viewfinder optical system are interlocked with each other by using a common cam tube. However, this arrangement has presented the following problems.
(i) The arrangement imposes design limitations on the layout of the photo-taking optical system and that of the viewfinder optical system.
(ii) In the case of a rear-focus type zoom lens of high magnification generally employed as a phototaking optical system for a video camera, it is difficult to ensure adequate precision of a cam arrangement or the like when mechanically interlocking the photo-taking optical system and the viewfinder optical system. Therefore, the arrangement lowers the optical performance of the photo-taking optical system.
The camera disclosed in Japanese Laid-Open Patent Application No. HEI 5-333406 is arranged to have the magnification varying action of the photo-taking optical system and that of the viewfinder optical system interlocked with each other. However, the magnification varying action of the viewfinder optical system is arranged to be performable independently of the photo-taking optical system. Therefore, in the mode of interlocking the magnification varying actions of these two optical systems, the driving motor of the photo-taking optical system is driven on the basis of data of the lens focal length of the photo-taking optical system computed from the lens position (focal length) of the viewfinder optical system and the magnification of electronic zooming. More specifically, the current lens position of the viewfinder optical system is detected with a zoom encoder by driving the driving motor of the viewfinder optical system and then the driving motor of the photo-taking optical system is driven on the basis of the focal length data of the lens of the photo-taking optical system corresponding to the current lens position detected. In other words, the magnification varying action of the photo-taking optical system is performed on the basis of the data of lens focal length corresponding to a lens position of the viewfinder optical system detected when a magnification varying action is performed. Therefore, for accurate control over the lens position of the photo-taking optical system to move it exactly to a desired position, the mechanism for detecting the lens position of the viewfinder optical system must be arranged to highly accurately act with a high degree of performance.
It is an object of the invention to provide an optical system driving control device which is capable of driving a photo-taking optical system and a viewfinder optical system in an accurately interlocked state.
To attain the above object, in accordance with an aspect of the invention, there is provided an optical system driving control device, which comprises (a) a photo-taking optical system including a photo-taking optical element which is movable in an optical axis direction thereof and first driving means for moving the photo-taking optical element in the optical axis direction thereof, (b) a viewfinder optical system including a viewfinder optical element which is movable in an optical axis direction thereof and second driving means for moving the viewfinder optical element in the optical axis direction thereof, and (c) control means for causing the first driving means and the second driving means to set the photo-taking optical element and the viewfinder optical element to respective initial positions thereof and, after that, to move the photo-taking optical element and the viewfinder optical element to respective predetermined positions where a ratio in magnification of the photo-taking optical element to the viewfinder optical element becomes a predetermined value.
The optical system driving control device is preferably provided with magnification varying action switching means for switching between a first mode in which the first driving means and the second driving means are driven in association with each other and a second mode in which the first driving means and the second driving means are driven independently of each other.
In accordance with another aspect of the invention, there is provided an optical system driving control device, which comprises a photo-taking optical system having a variable magnification, a viewfinder optical system having a variable magnification, instruction means for giving an instruction for recording an image formed by the photo-taking optical system, and control means for controlling a magnification varying action of the photo-taking optical system and that of the viewfinder optical system, the control means providing control including a first step of performing only the magnification varying action of the viewfinder optical system and a second step of performing the magnification varying action of the photo-taking optical system to move the photo-taking optical system to a magnification varying position corresponding to a magnification varying position of the viewfinder optical system obtained by the first step, wherein the control provided by the control means shifts from the first step to the second step when the instruction for recording the image is given by the instruction means.
In accordance with a further aspect of the invention, there is provided a camera, which comprises a photo-taking optical system, an image sensor arranged to convert into an electrical signal an image formed by the photo-taking optical system, means for providing an electronic magnification varying zone where a part of the image is electronically magnified, and a viewfinder optical system having a variable magnification, an optical magnification varying zone of the viewfinder optical system encompassing the electronic magnification varying zone, and variation of magnification of the viewfinder optical system being performed by a driving mechanism arranged independently of the photo-taking optical system.